Re: [PATCH] Add "riscv" as an alias for "riscv32"

[John Ericson]

Ah OK. So this boils down to the difference between configs for targets 
and configs for toolchains. Configs for targets should be precise as 
possible [1], and `riscv-*` makes no sense. Configs for tools are 
actually the *set* of configs the tool targets and so `riscv-` does 
indeed make make perfect sense [2]. So we can add a flag to gnu config 
(with sensible default) to only allow stuff like this for the latter 
tool case. We could also choose to add another shell script answering 
"does (tool) config a cover config b", codifying that relation. I would 
volunteer to do both of these things if a RISC-V person can give me a 
table with the intend relation.

I agree with the gist of what Earnie says. To preserve symmetry and not 
surprise the user with weird defaults, I'd say a `riscv-*` tool-chain 
shouldn't default to 32-bit, 64-bit, or anything else. So the `-m64` or 
whatever is required. Or perhaps to make native compilation a bit easier 
a RISC-V tool chain should *only* default to a specific variant of 
RISC-V if that platform is the host platform, so cross compilation must 
be explicit, but native compilation with explicit-config tools can be 
implicit.

John

[1] Configs for targets are more known with LLVM than GNU tools, and 
their `-target` flag. But certain GNU binutils (e.g. objdump) do support 
`--target` so it's not just an LLVMism.
[2] Yet another example of autotools and friends forcing a single target 
platform muddying the waters.

On 06/21/18 13:49, Earnie wrote:
> On 6/20/2018 7:55 PM, Palmer Dabbelt wrote:
> > The one saving grace here is that most of the RISC-V toolchains support
> > generating code for all targets -- in other words "riscv32-*-gcc
> > -march=rv64gc" is a valid thing to do, and will generate 64-bit code
> > (and links against a 64-bit libc).  As a result, none of this actually
> > matters.
> Given this I can understand the frustration of needing the 32/64
> specifier.  I would then suggest the patch removes riscv32 and riscv64
> specifics and use riscv* instead.  I.E. use riscv*-* as the filter.